Growth and fabrication of GaN/AlGaN heterojunction bipolar transistor

A GaN/AlGaN heterojunction bipolar transistor structure with Mg doping in the base and Si doping in the emitter and collector regions was grown by metalorganic chemical vapor deposition on c-axis Al2O3. Secondary ion mass spectrometry measurements showed no increase in the O concentration (2-3 x 10(18) cm(-3)) in the AlGaN emitter and fairly low levels of C (similar to 4 - 5 x 10(17) cm(-3)) throughout the structure. Due to the nonohmic behavior of the base contact at room temperature, the current gain of large area (similar to 90 mm diameter) devices was <3. Increasing the device operating temperature led to higher ionization fractions of the Mg acceptors in the base, and current gains of similar to 10 were obtained at 300 degrees C. (C) 1999 American Institute of Physics. [S0003-6951(99)02218-4].